Optics formation using pick-up tools

ABSTRACT

Techniques related to optics formation using pick-up tools are disclosed. Optical elements are formed by pressing a pick-up tool (PUT) against elastomeric material deposited on a light-outputting side of light-emitting diode (LED) devices. Pressing the PUT against the elastomeric material causes a molded shape of the PUT to be transferred to the elastomeric material. This forms the optical elements in the elastomeric material.

BACKGROUND

The disclosure relates generally to semiconductor device fabrication,and more specifically to formation of optical elements on semiconductordevices.

Semiconductor devices have become prevalent in electronics for providingsuch benefits as reduced size, improved durability, and increasedefficiency. For example, in contrast to an incandescent light bulb, alight-emitting diode (LED) is typically smaller, lasts several timeslonger, and converts proportionately more energy into light instead ofheat. Accordingly, semiconductor devices have even been incorporatedinto display systems, such as those found in televisions, computermonitors, laptop computers, tablets, smartphones, and wearableelectronic devices. In particular, tiny LEDs can be used to form thesub-pixels of a display system. However, manipulating such tiny LEDs canbe challenging. Furthermore, the brightness of such tiny LEDs can belimited by their size.

SUMMARY

This disclosure relates to the formation of optical elements onsemiconductor devices. In some embodiments, the semiconductor devicesare LEDs having elastomeric material deposited thereon. The elastomericmaterial enables a pick-up tool (PUT) to adhere to the LEDs, which canbe transported by the PUT onto a target substrate. The elastomericmaterial can also be molded into optical elements that increase thebrightness of the LEDs.

Disclosed herein are techniques related to concurrently picking up theLEDs and forming optical elements on the LEDs. This can be achievedusing a PUT having a pick-up surface that is adapted for molding opticalelements. For example, the PUT may have one or more cavities that eachhave the shape of an optical element. Thus, pressing the PUT againstelastomeric material not only causes the PUT to adhere to theelastomeric material, but also forms one or more optical elements in theelastomeric material.

Advantageously, the techniques disclosed herein can reduce sources oferror in the fabrication process. For example, errors may be introducedby performing alignment for device pick-up separately from performingalignment for optics formation. Thus, performing alignment once for bothdevice pick-up and optics formation can reduce errors.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments are described with reference to the followingfigures.

FIG. 1 illustrates an example semiconductor device, in accordance withan embodiment.

FIGS. 2A-D illustrate an example approach for forming elastomericinterfaces on semiconductor devices, in accordance with an embodiment.

FIGS. 3A-B illustrate an example approach for picking up and placingsemiconductor devices, in accordance with an embodiment.

FIGS. 4A-B illustrate an example approach for molding optical elementson semiconductor devices, in accordance with an embodiment.

FIGS. 5A-D illustrate an example approach for molding optical elementsusing a pick-up tool, in accordance with an embodiment.

FIGS. 6A-B illustrate an example approach for removing excesselastomeric material, in accordance with an embodiment.

FIG. 7 is a flow diagram illustrating an example approach for formingoptical elements on semiconductor devices, in accordance with anembodiment.

FIG. 8 illustrates an example fabrication system, in accordance with anembodiment.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated may be employed without departing from theprinciples, or benefits touted, of this disclosure.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, specificdetails are set forth in order to provide a thorough understanding ofcertain inventive embodiments. However, it will be apparent that variousembodiments may be practiced without these specific details. The figuresand description are not intended to be restrictive.

Disclosed herein are techniques that enable error reduction duringfabrication of semiconductor devices, such as LEDs and photodiodes. Insome embodiments, the fabricated semiconductor devices are tinyinorganic LEDs known as microLEDs having optical elements formedthereon. Example optical elements include, without limitation, a lens, awaveguide, and/or a diffraction grating. As used herein, a microLED mayrefer to an LED that has an active light-emitting area with a lineardimension that is less than 50 μm, less than 20 μm, or less than 10 μm.For example, the linear dimension may be as small as 2 μm or 4 μm.

Semiconductor Devices

Referring to FIG. 1, a cross-sectional view of an example semiconductordevice is provided. More specifically, the semiconductor device is anexample of a microLED 100. As used herein, a microLED may refer to anLED that has an active light-emitting area with a linear dimension thatis less than 50 μm, less than 20 μm, or less than 10 μm. For example,the linear dimension may be as small as 2 μm or 4 μm. Their small sizeenables a display system to have a single pixel comprising three ofthem: a red micro LED, a green micro LED, and a blue micro LED. Theirsmall size also enables micro LEDs to be lightweight, making themparticularly suitable for use in wearable display systems, such aswatches and computing glasses.

The microLED 100 includes, among other components, a semiconductorstructure. The semiconductor structure comprises semiconductor layers102-104 and a light-emitting layer 106 that sits between thesemiconductor layers 102-104. For example, the microLED 100 may comprisea semiconductor structure in which the light-emitting layer 106 is alayer of indium gallium nitride that is sandwiched between a layer ofp-type gallium nitride and a layer of n-type gallium nitride. In someembodiments, semiconductor layer 102 is a p-type semiconductor, andsemiconductor layer 104 is an n-type semiconductor. In some embodiments,semiconductor layer 102 is an n-type semiconductor, and semiconductorlayer 104 is a p-type semiconductor.

The semiconductor layers 102-104 are operatively coupled to electricalcontacts 108-110, respectively. The electrical contacts 108-110 aretypically made of a conductive material, such as a metallic material. Inthe example of FIG. 1, the electrical contacts 108-110 are both locatedon a top surface of the semiconductor structure such that they can bothsupport the microLED 100 when it is mounted on a substrate including acontrol circuit. However, in some embodiments, electrical contacts canbe located on opposite surfaces of a semiconductor structure.

The light-emitting layer 106 includes one or more quantum wells thatoutput light 116 when a voltage is applied across the electricalcontacts 108-110. To directionalize the output of light 116, thesemiconductor structure may be formed into any of a variety of shapes(e.g., a paraboloid, a cylinder, or a cone) that enablecollimation/quasi-collimation of light 116. Such shapes are referred toherein as “mesa” shapes; and collimation and quasi-collimation arecollectively referred to herein as “collimation”. Collimation results inincreased brightness of light output.

In the example of FIG. 1, mesa 114 corresponds to a paraboloid shapethat guides light 116 toward through a light-emitting surface 112 of thesemiconductor structure. More specifically, the light-emitting layer 106is approximately positioned at the focal point of the paraboloid suchthat some of the emitted light is reflected, within a critical angle oftotal internal reflection, off the inner walls of the paraboloid towardthe light-emitting surface 112.

In some embodiments, a mesa shape also has a truncated top that canaccommodate an electrical contact. In the example of FIG. 1, mesa 114corresponds to a paraboloid shape having a truncated vertex thataccommodates electrical contact 108. Base 118 refers to the part of thesemiconductor structure that is not included in the mesa 114.

To enable further collimation of light 116, an optical element 120 canbe formed on the light-emitting surface 112. In the example of FIG. 1,the optical element 120 is a microlens. As will be described in greaterdetail below, the optical element 120 can be formed from elastomericmaterial that both (a) facilitates adhesion with a PUT and (b) hassuitable optical properties.

The microLED 100 may include other components, such as a dielectriclayer, a reflective layer, and a substrate layer. However, to avoidobscuring the disclosure, such components are not illustrated in FIG. 1.

Formation of Patterned Elastomeric Layer

Elastomeric material may be deposited on a set of one or moresemiconductor devices to enable (a) forming optical elements on the setand/or (b) picking up the set using a PUT. The elastomeric material maybe deposited on all or part of a particular side/surface of the set. Forexample, if the set comprises one or more LED devices, the elastomericmaterial may be deposited on all or part of a light-outputting side(e.g., light-emitting surface 112) of the set. However, it isunnecessary for the elastomeric material to extend beyond the particularside/surface of the set. Thus, at least some of the unnecessaryelastomeric material can be removed from regions between different setsof one or more semiconductor devices. FIGS. 2A-D illustrate an exampleprocess for removing such material to form a “patterned” layer ofelastomeric material.

As used herein, “patterning” refers to removing one or more regions froma layer of material such that remaining regions of the layer form adesired pattern. The desired pattern corresponds to an arrangement ofsemiconductor devices. For example, if individual semiconductor dies arearranged in a 3×3 grid, then a layer of material may be patterned tomirror the grid arrangement. This can be achieved based on singulatingthe layer of material according to the grid arrangement of the dies. Asanother example, if arrays of unsingulated semiconductor devices arearranged in a 1×3 grid, then a layer of material may be patterned basedon removing regions of the layer positioned over gaps between arrays.

“Patterning” can be performed using a layered structure, such as the oneillustrated in the example of FIG. 2A. The layered structure 200comprises a photoresist layer 216, an elastomeric layer 214, an embeddedlayer 204, and an optional handle layer 202. The layered structure 200may be obtained based on forming and/or depositing the layers, in order,on top of the handle layer 202. For example, the embedded layer 204 maybe formed on the handle layer 202, the elastomeric layer 214 may then bedeposited on the embedded layer 204, and the photoresist layer 216 maythen be deposited on the elastomeric layer 214.

The handle layer 202 may be a substrate composed of glass, silicon, orany other transparent/quasi-transparent material. The handle layer 202may facilitate transportation of all or part of the layered structure200.

The embedded layer 204 comprises sets 206-210 of one or moresemiconductor devices embedded in a filling material 212. Although FIG.2A illustrates the semiconductor devices as being completely embedded inthe filling material 212, at a minimum, the filling material 212 is usedto fill in the gaps between different sets 206-210 of one or moresemiconductor devices.

In the example of FIG. 2A, each set consists of a single semiconductordevice.

However, in some embodiments, each set is an array of unsingulatedsemiconductor devices. Although the semiconductor devices illustrated inFIGS. 2A-D are abstractions of LED devices, it should be appreciatedthat the techniques disclosed herein are equally applicable to any othersemiconductor devices. Furthermore, although only three semiconductordevices are illustrated in each of FIGS. 2A-D, it should be appreciatedthat the techniques described herein are equally applicable to anynumber of semiconductor devices.

The filling material 212 can be formed on the handle layer 202 afterplacement of the semiconductor devices on the handle layer 202. Forreasons that will become apparent below, the filling material 212 is notformed on top of the semiconductor devices. Thus, the semiconductordevices are embedded in the filling material 212 such that the topsurfaces of the filling material 212 are flush with the top surfaces ofthe semiconductor devices. The filling material 212 can be any of avariety of polymers including, without limitation, polyvinyl alcohol,polyvinyl acetate, polyester, polymethyl methacrylate, polystyrene,polycarbonate, or polyvinyl butyral.

The elastomeric layer 214 may be composed of a viscoelastic polymer,such as polydimethylsiloxane (PDMS) or polyurethane, that istransparent/quasi-transparent. The conformable material in theelastomeric layer 214 can adhere to a PUT surface composed of anon-conformable material, such as fused silica, sapphire, etc. Adhesioncan be achieved based on exploiting weak intermolecular forces, such asVan der Waals forces. In some embodiments, the elastomeric layer 214also exhibits optical properties including, without limitation, atunable refractive index and/or temporal stability (e.g., about 30,000hours at or below 80 degrees Celsius). The elastomeric layer 214 may bedeposited on the embedded layer 204 using any of a variety oftechniques, such as spin-coating.

The photoresist layer 216 may be composed of a photosensitive polymerwhich, when exposed to light within a particular wavelength range,becomes soluble to a photoresist developer. In some embodiments, theelastomeric layer 214 is made hydrophilic prior to depositing thephotoresist layer 216 thereon. This can be achieved using any of avariety of techniques, such as treatment of the elastomeric layer 214with oxygen plasma. A hydrophilic elastomeric layer 214 facilitatesuniform deposition of the photoresist layer 216.

Referring to FIG. 2B, the photoresist layer 216 of FIG. 2A is structuredto form a patterned photoresist layer 220. Patterning the photoresistlayer 216 involves transmitting light 218 through the elastomeric layer214 toward the photoresist layer 220 (e.g., in a bottom-to-topdirection). Doing so uses the sets 206-210 as a light mask that blockslight from reaching the photoresist layer 216. Thus, light 218 reachesthe photoresist layer 216 via the filling material 212 that separatesthe sets 206-210. Regions of the photoresist layer 216 exposed to light218 become soluble and are washed away using a photoresist developer.Light 218 typically has a wavelength that falls within a range that isstrongly absorbed by the semiconductor material. For example, when thesemiconductor material is gallium nitride, light 218 may have awavelength that falls within the ultraviolet range (e.g., less than 360nanometers) of the electromagnetic spectrum, because wavelengths in thatrange are strongly absorbed by gallium nitride. This enables thesemiconductor material to serve as masking material against the light218.

In the example of FIG. 2B, the patterned photoresist layer 220 comprisesthree remaining regions of the photoresist layer 216. Significantly,these remaining regions have shapes that are substantially similar, ifnot identical, to those of the sets 206-210 used as a light mask.

Referring to FIG. 2C, the elastomeric layer 214 of FIG. 2B is structuredto form a patterned elastomeric layer 224. Patterning the elastomericlayer 214 can be achieved based on an etching process in which thepatterned photoresist layer 220 is used as an etch mask. The etchingprocess may involve one or more etching techniques, such as dry etching,wet etching, or combinations thereof. In the example of FIG. 2C, theetching process involves an anisotropic dry etching technique using anetchant 222. Examples of dry etching techniques include, withoutlimitation, Radio Frequency (RF) oxygen plasma etching, reactive ionetching (ME), and/or inductively coupled plasma (ICP) etching.

In some embodiments, the etchant 222 comprises a plasma mixture ofsulfur hexafluoride and oxygen that is used to perform an ICP etch.Significantly, the etchant 222 is accelerated in a direction (e.g., atop-to-bottom direction) that is opposite to the direction in whichlight 218 was transmitted during formation of the patterned photoresistlayer 220. Thus, the patterned photoresist layer 220 can be used as anetch mask that protects underlying regions of the elastomeric layer 214from the etchant 222. In other words, the patterned photoresist layer220 leaves unprotected regions of the elastomeric layer 214 to be erodedby the etchant 222. In the example of FIG. 2C, the resulting patternedelastomeric layer 224 comprises three remaining regions of theelastomeric layer 214. Significantly, these remaining regions haveshapes that are substantially similar, if not identical, to those of thesets 206-210.

All or part of the patterned photoresist layer 220 may be eroded duringthe aforementioned etching process. The amount of patterned photoresistlayer 220 allowed to remain after the etching process may depend on thetechnique used to remove the filling material 212. In the example ofFIG. 2D, further etching is performed to remove the filling material212. Thus, some or all of the patterned photoresist layer 220 remains onthe patterned elastomeric layer 224 to protect the underlying patternedelastomeric layer 224.

Referring to FIG. 2D, an etchant 226 is used to etch the fillingmaterial 212 of FIG. 2C. The etchant 226 may be the same or differentfrom the etchant 222. In the example of FIG. 2D, the etchant 226comprises oxygen plasma for performing RF oxygen plasma etching. In someembodiments, the patterned photoresist layer 220 is completely erodedupon removal of the filling material 212. In some embodiments, anyremnants of the patterned photoresist layer 220 are subsequently removedin a separate process. When the patterned photoresist layer 220 iscompletely eroded or otherwise removed, elastomeric interfaces 228-232are revealed.

Significantly, the aforementioned techniques enable consistent andefficient formation of elastomeric interfaces 228-232 having shapes thatare substantially similar, if not identical, to those of sets 206-210.In contrast, conventional techniques may result in elastomericinterfaces 228-232 that are misshapen and/or misaligned relative to sets206-210. For example, some conventional techniques may form thepatterned photoresist layer 220 in a separate photolithography processthat introduces errors.

As will be described in greater detail below, elastomeric interfaces228-232 enable semiconductor devices to interface with a PUT and/or anoptics mold.

Pick-and-Place

FIGS. 3A-B illustrate an example pick-and-place process for transportingsemiconductor devices from one substrate to another. A pick-and-placeprocess is often used in the electronics industry for mountingsemiconductor devices on a printed circuit board based on manipulatingindividual sets of one or more semiconductor devices. For example, apick-and-place process may be used for assembling a display system basedon positioning LEDs onto designated pixel locations.

Referring to FIG. 3A, sets 302-306 are positioned on substrate 300,which may facilitate transportation of the sets 302-306 between stationsof a fabrication system. For example, the substrate 300 may be used totransport the sets 302-306 from an epitaxial growth station to apick-and-place station. Each set of the sets 302-306 comprises one ormore semiconductor devices. Interfaces 308-312 are respectivelypositioned on the sets 302-306. The interfaces 308-312 may be composedof any material suitable for a pick-and-place process. For example, theinterfaces 308-312 may be composed of a conformable material thatadheres to a non-conformable pick-up surface.

In some embodiments, FIG. 3A illustrates the result of removing thepatterned photoresist layer 220 of FIG. 2D. In other words, thesubstrate 300 may be the handle layer 202, the sets 302-306 may be thesets 206-210, and the interfaces 308-312 may be the interfaces 228-232.

Referring to FIG. 3B, a pick-up tool 314 is used to transport the set302 from the substrate 300 to a target substrate 316. In someembodiments, the target substrate 316 comprises circuitry for operatingthe set 302. For example, the target substrate 316 may comprise aprinted circuit board for a display system. A scanning electronmicroscope (SEM) or some other visual feedback system (not shown) mayfacilitate alignment of the set 302 with a desired position on thesubstrate 316.

Transportation of the set 302 is enabled by adhesion between the pick-uptool 314 and the interface 308. In some embodiments, the interface 308adheres to the pick-up tool 314 based on forming weak intermolecularbonds. In general, adhesion forces increase in strength with an increasein the contact surface between the interface 308 and the pick-up tool314.

Optics Formation

FIGS. 4A-B illustrate an example process for forming optical elements onsemiconductor devices. Each optical element may correspond to adifferent semiconductor device. As mentioned above, optical elements maybe formed on light-emitting surfaces of LEDs to enable furthercollimation of light. Thus, such optical elements may be referred to as“secondary optics”, where “primary optics” refer to mesa-shapedsemiconductor structures.

Referring to FIG. 4A, sets 402-406 are positioned on substrate 400. Eachset of the sets 402-406 comprises one or more semiconductor devices. Inthe example of FIG. 4A, each set consists of a single semiconductordevice. However, in some embodiments, each set is an array ofunsingulated semiconductor devices. Although FIG. 4A illustrates threesets, it should be appreciated that the techniques described herein areequally applicable to any number of sets.

In some embodiments, the substrate 400 may be the target substrate 316of FIG. 3B. Thus, the sets 402-406 may have been subjected to apick-and-place process involving interfaces 408-412. The sets 402-406may be transported to the substrate 400 from a plurality of substratescomprising a red LED substrate, a green LED substrate, and a blue LEDsubstrate.

One or more optical elements may be formed on each set of the sets402-406 based on pressing a mold 414 against each interface of theinterfaces 408-412. A SEM or some other visual feedback system (notshown) may facilitate alignment of the mold 414 with a particularinterface. In particular, alignment may be performed based on leveragingphotoluminescence properties of some semiconductor devices, such asLEDs. More specifically, such a semiconductor device can be irradiatedwith ultraviolet light, thereby exciting the semiconductor device intoemitting fluorescent light. This fluorescent light can be aligned to thecenter of an optics formation cavity in the mold 414. Thus, the centerof an optical element can be more precisely aligned with the center of alight-emitting region of a semiconductor device.

Although the mold 414 is illustrated in the example of FIG. 4A as havingonly one molded shape, in some embodiments, the mold 414 has a pluralityof molded shapes. Each molded shape of the mold 414 is a cavity having a“negative” image of an optical element. Thus, when the mold 414 ispressed against an interface of the interfaces 408-412, the mold 414transfers each molded shape to the interface, thereby forming a“positive” image of the optical element in the interface. As usedherein, a negative image refers to an image that isinverted/recessed/debossed relative to its environment, whereas apositive image refers to an image that is raised/embossed relative toits environment.

As mentioned above, the interfaces 408-412 may be composed of aconformable material, such as PDMS or some other elastomeric material.The mold 414 can be made of any of a variety of materials that havesuperior structural robustness relative to the interfaces 408-412. Forexample, the interfaces 408-412 are composed of a conformable material,and the mold 414 may be composed of a non-conformable material, such asglass or fused silica.

Referring to FIG. 4B, an optical element 416 is revealed when the mold414 is separated from the interface 408. Molding the optical element 416in the interface 408 can be facilitated by heating the interface 408.For example, heating the substrate 400 may cause the interface 408 to beheated to a high temperature (e.g., 270 degrees Celsius) thatfacilitates imprinting. However, when the substrate 400 is a componentof a display system, heating the substrate 400 to a high temperature maydamage the display system.

Concurrent Pick-and-Place and Optics Formation

FIGS. 5A-D illustrate an example process for performing pick-and-placeconcurrently with optic(s) molding. For the sake of clarity and ease ofexplanation, FIGS. 5A-D illustrate a single set of three semiconductordevices. However, it should be appreciated that the techniques describedherein are equally applicable to any number of sets comprising anynumber of semiconductor devices.

Referring to FIG. 5A, a set of semiconductor devices 502 is positionedon a substrate 500. The substrate 500 may be the substrate 300 of FIGS.3A-B and/or the handle layer 202 of FIGS. 2A-D. The set of semiconductordevices 502 has an interface 504 deposited on a light-outputting side ofthe set (e.g., the top side). The interface 504 may be any of theaforementioned interfaces (e.g., the interfaces 228-232 of FIG. 2D, theinterfaces 308-312 of FIGS. 3A-B, and/or the interfaces 408-412 of FIG.4A).

A pick-up tool 506 is pressed against the interface 504. A SEM or someother visual feedback system (not shown) may facilitate alignment of thepick-up tool 506 with the interface 504. As mentioned above, alignmentmay be performed based on leveraging photoluminescence properties ofsome semiconductor devices, such as LEDs. All or part of the pick-uptool 506 may be composed of a transparent/quasi-transparent materialthrough which ultraviolet light may be transmitted toward asemiconductor device. The fluorescent light emitted from thesemiconductor device may be aligned to the center of a cavity in thepick-up tool 506. Significantly, the pick-up tool 506 performs thefunctions of both the pick-up tool 314 of FIG. 3B and the mold 414 ofFIGS. 4A-B. Thus, it is unnecessary to perform separate alignments for(a) pick-and-place and (b) optics formation. Advantageously, thisreduces errors caused by misalignment.

The pick-up tool 506 has molded shapes that are transferred to theinterface 504 when the pick-up tool 506 is pressed against the interface504. In some embodiments, the interface 504 is composed of a conformablematerial, and at least a pick-up surface of the pick-up tool 506 iscomposed of a non-conformable material. Although FIG. 5A illustrates thepick-up tool 506 as having three molded shapes, it should be appreciatedthat the pick-up tool 506 can have any number of molded shapes,including one molded shape.

Referring to FIG. 5B, optical elements 508 are formed in the interface504 when the pick-up tool 506 is pressed against the interface 504. Thenumber of optical elements 508 that are formed corresponds to the numberof molded shapes in the pick-up tool 506. Furthermore, the number ofoptical elements 508 corresponds to the number of semiconductor devices502.

In some embodiments, formation of the optical elements 508 isfacilitated by heating the interface 504 to a high temperature. This canbe achieved based on using a hot plate to apply heat to the substrate500 and/or using laser light (e.g., ultraviolet light that is convertedinto heat when absorbed) to irradiate the layer of semiconductormaterial in contact with the interface 504. Significantly, by heatingthe interface 504 prior to placing the devices 502 on a display system,damaging the display system is avoided.

Referring to FIG. 5C, pressing the pick-up tool 506 against theinterface 504 also causes the pick-up tool 506 to adhere to theinterface 504 in which the optical elements 508 have been formed. Thisenables the devices 502 to be picked up and placed on a substrate 510.In some embodiments, the substrate 510 is a component of a displaysystem that incorporates the devices 502.

Referring to FIG. 5D, the pick-up tool 506 is separated from theinterface 504 in which the optical elements 508 have been formed. Doingso reveals the optical elements 508 that enable increased lightcollimation. Separating the pick-up tool 506 from the interface 504 alsoenables light to emanate from the optical elements 508 when a voltage isapplied across the devices 502.

Removal of Excess Interface Material

FIGS. 6A-B illustrate an example process for removing excess materialsurrounding one or more optical elements. The excess material may havethe undesirable effect of scattering light. Furthermore, in an array ofunsingulated LEDs, the excess material may have the undesirable effectof causing cross-talk between pixels. Thus, it is beneficial to removeas much of the excess material as possible.

Referring to FIG. 6A, a set of semiconductor devices 602 is positionedon a substrate 600. Optical elements 604 are formed on the devices 602.FIG. 6A may illustrate the result of performing the process of FIGS.4A-B or FIGS. 5A-D.

Referring to FIG. 6B, excess material is removed from one or moreregions surrounding optical elements 606-610. This may be achieved basedon an etching process.

Process Overview

FIG. 7 illustrates an example process for forming optical elements witha PUT. In some embodiments, the example process is performed at astation of a fabrication system that incorporates LEDs into displaysystems.

At block 700, the station obtains a set of one or more LED deviceshaving one or more elastomeric interfaces deposited on alight-outputting side of the set. In some embodiments, the set comprisesa plurality of unsingulated LED devices. One or more other stations mayhave produced the set from a layered structure according to the processillustrated in FIGS. 2A-D.

More specifically, the process of FIGS. 2A-D involves the one or moreother stations obtaining the layered structure. The layered structuredincludes an embedded layer, an elastomeric layer, and a photoresistlayer. The embedded layer comprises multiple sets of one or more LEDdevices embedded in a filling material. The elastomeric layer isdeposited on the embedded layer. The photoresist layer is deposited onthe elastomeric layer.

The process of FIGS. 2A-D also involves the one or more other stationspatterning the photoresist layer by using the multiple sets of one ormore LED devices as a mask in a first direction. This may involvetransmitting light through the elastomeric layer toward the photoresistlayer.

Furthermore, the process of FIGS. 2A-D involves the one or more otherstations patterning the elastomeric layer using the patternedphotoresist layer as a mask in a second direction that is opposite thefirst direction. This may involve etching the elastomeric layer.

After patterning the elastomeric layer, the one or more other stationsmay remove the filling material and the patterned photoresist layer.This reveals the multiple sets of one or more LED devices having thepatterned elastomeric layer deposited thereon.

At block 702, the station causes a PUT to be pressed against the one ormore elastomeric interfaces. This causes the PUT to adhere to the one ormore elastomeric interfaces. This also causes the PUT to transfer one ormore molded shapes of the PUT to the one or more elastomeric interfaces.Thus, one or more optical elements are formed in the one or moreelastomeric interfaces. The one or more optical elements include atleast one of a group comprising a lens, a waveguide, and a diffractiongrating. Each optical element corresponds to a respective LED device ofthe set.

At block 704, the station uses the PUT to pick up and place the set ontoa target substrate. This is enabled by the adhesion between the PUT andthe one or more elastomeric interfaces.

At block 706, the station separates the PUT from the one or moreelastomeric interfaces. This reveals the one or more optical elements onthe set.

In some embodiments, elastomeric material surrounding the one or moreoptical elements may be removed from the one or more elastomericinterfaces.

System Overview

FIG. 8 illustrates an example fabrication system. In some embodiments,the fabrication system comprises a station that incorporates LED devicesinto a display system. The fabrication system includes a chamber 800that defines an interior environment for incorporating LED devices intoa display system. The chamber 800 houses various system componentsincluding a pick-up tool 802; a controller 804; actuator(s) 806; anetcher 812; substrates 816 and 828; stages 814 and 826; and a laser 824.The chamber 800 may also house other system components not illustratedin FIG. 8. For example, the chamber 800 may also house a SEM in a highpressure atmosphere of water vapor.

It should be appreciated that the example fabrication system of FIG. 8is merely provided as an illustrative and non-limiting example and thatone or more components may be modified, removed, or added to the examplefabrication system without departing from the scope of the disclosure.For example, the embodiment illustrated in FIG. 8 may be practiced witha collimated lamp or some other light source instead of the laser 824.Different implementations may use different light sources so long aslight within a suitable wavelength range is proviced. For example, whenthe LED devices are composed of gallium nitride, a laser or a collimatedlamp may be used to provide light in the ultraviolet wavelength range(e.g., having emission line wavelengths lower than 360 nanometers) ofthe electromagnetic spectrum.

The substrate 816 serves as a carrier for a layered structure comprisingan embedded layer 818, an elastomeric layer 820, and a photoresist layer822. The substrate 816 can be any of a variety of materials on which thelayered structure can be carried. Example materials include, withoutlimitation, glass, silicon, or some other transparent/quasi-transparentmaterial through which light (e.g., ultraviolet light) can betransmitted.

In the example of FIG. 8, the embedded layer 818 comprises two arrays ofLED devices, each array having two unsingulated LED devices. Typically,the LED devices in each array emit light of the same color. In contrastto singulated LED devices, arrays of unsingulated LED devices offer thebenefit of facilitating alignment processes. More specifically, it iseasier to align a relatively large array of devices than to align anindividual device that is relatively small.

The stage 814 holds the substrate 816. The stage 814 may be movable in avariety of directions including, without limitation, up and down; leftand right; and forward and back.

The laser 824 transmits light for patterning the photoresist layer 822.For example, a laser beam may be transmitted through the substrate 816,embedded layer 818, and elastomeric layer 820. The embedded layer 818filters some of the light such that only some regions of the photoresistlayer 822 are exposed to the light. These regions can be washed away toform a pattern in the photoresist layer 822. In some embodiments, thelaser 824 is incorporated into the stage 814.

As mentioned above, instead of using the laser 824, some fabricationsystems may use a collimated lamp or some other light source to patternthe photoresist layer 822. Thus, the particular light source that isused may vary from implementation to implementation so long as light inan appropriate wavelength range is provided. For example, when the LEDdevices are composed of gallium nitride, any source of ultraviolet light(e.g., having a wavelength of less than 360 naometers) may be used.

The etcher 812 erodes regions of the elastomeric layer 820 based oninstructions received from the controller 804. More specifically, theetcher 812 bombards the elastomeric layer 820 with plasma, some of whichis blocked by the patterned photoresist layer 822. Regions of theelastomeric layer 820 that are not protected by the patternedphotoresist layer 822 are eroded such that elastomeric interfaces areformed.

The etcher 812 may include gas intake and gas out-take valves, ionizingplates, and any other standard etching components. In some embodiments,the etcher 812 is also used to remove the patterned photoresist layer822 to reveal the underlying elastomeric interfaces.

The pick-up tool 802 is pressed against an elastomeric interface to pickup and place devices 830 on the substrate 828. The substrate 828 maycomprise circuitry for a display system. The stage 826 holds thesubstrate 828 and is movable in a variety of directions including,without limitation, up and down; left and right; and forward and back.

Furthermore, the pick-up tool 802 has a surface with molded shapes forforming optical elements. Thus, pressing the pick-up tool 802 against anelastomeric interface also causes optical elements to be formed on thedevices 830.

The pick-up tool 802 is operatively coupled to the actuator(s) 806. Theactuator(s) 806 electromechanically control the movement of the pick-uptool 802 based on instructions from the controller 804. The actuator(s)806 may move the pick-up tool 802 in a variety of directions including,without limitation, up and down; left and right; and forward and back.Examples of actuator(s) 806 include, without limitation, a rotatingmotor, a linear motor, and/or a hydraulic cylinder.

The controller 804 is coupled, via the actuator(s) 806, to the pick-uptool 802 and controls the operations of the pick-up tool 802. Thecontroller 804 may include, among other components, a memory 810 andprocessor(s) 808. The memory 810 stores instructions for operating thepick-up tool 802. The memory 810 may be implemented using any of avariety of volatile or non-volatile computer-readable storage mediaincluding, without limitation, SRAM, DRAM, and/or ROM. The processor(s)808 execute the instructions stored in the memory 810 and sendinstructions toward the pick-up tool 802. In some embodiments, theprocessor(s) 808 execute the example process illustrated in FIG. 7.

Embodiments of the invention may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,and any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g.,perform activities in) an artificial reality. The artificial realitysystem that provides the artificial reality content may be implementedon various platforms, including a head-mounted display (HMD) connectedto a host computer system, a standalone HMD, a mobile device orcomputing system, or any other hardware platform capable of providingartificial reality content to one or more viewers.

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of thedisclosure in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like. Furthermore, it has also proven convenient attimes, to refer to these arrangements of operations as modules, withoutloss of generality. The described operations and their associatedmodules may be embodied in software, firmware, and/or hardware.

Steps, operations, or processes described may be performed orimplemented with one or more hardware or software modules, alone or incombination with other devices. In some embodiments, a software moduleis implemented with a computer program product comprising acomputer-readable medium containing computer program code, which can beexecuted by a computer processor for performing any or all of the steps,operations, or processes described.

Embodiments of the disclosure may also relate to an apparatus forperforming the operations described. The apparatus may be speciallyconstructed for the required purposes, and/or it may comprise ageneral-purpose computing device selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a non-transitory, tangible computer readable storagemedium, or any type of media suitable for storing electronicinstructions, which may be coupled to a computer system bus.Furthermore, any computing systems referred to in the specification mayinclude a single processor or may be architectures employing multipleprocessor designs for increased computing capability.

Embodiments of the disclosure may also relate to a product that isproduced by a computing process described herein. Such a product maycomprise information resulting from a computing process, where theinformation is stored on a non-transitory, tangible computer readablestorage medium and may include any embodiment of a computer programproduct or other data combination described herein.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the disclosure be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

1. A method comprising: obtaining a set of one or more light-emittingdiode (LED) devices having one or more elastomeric interfaces depositedon a light-outputting side of the set of one or more LED devices; usinga pick-up tool to: form one or more optical elements in the one or moreelastomeric interfaces by pressing the pick-up tool against the one ormore elastomeric interfaces; and pick up and place the set of one ormore LED devices onto a target substrate; separating the pick-up toolfrom the one or more elastomeric interfaces, thereby revealing the oneor more optical elements formed on the set of one or more LED devices.2. The method of claim 1, wherein the one or more optical elements areformed in the one or more elastomeric interfaces before the set of oneor more LED devices is picked up and placed onto the target substrate.3. The method of claim 1, wherein the one or more optical elements areformed in the one or more elastomeric interfaces after the set of one ormore LED devices is picked up but as the set of one or more LED devicesis being placed onto the target substrate.
 4. (canceled)
 5. The methodof claim 1, further comprising: removing, from the one or moreelastomeric interfaces, elastomeric material surrounding the one or moreoptical elements.
 6. The method of claim 1, wherein the set of one ormore LED devices comprises a plurality of unsingulated LED devices. 7.The method of claim 1, wherein the set of one or more optical elementsincludes at least one of a group comprising a lens, a waveguide, and adiffraction grating.
 8. The method of claim 1, wherein obtaining the setof one or more LED devices having the one or more elastomeric interfacescomprises: obtaining a layered structure that includes an embedded layercomprising multiple sets of one or more LED devices embedded in afilling material, an elastomeric layer deposited on the embedded layer,and a photoresist layer deposited on the elastomeric layer; patterningthe photoresist layer by using the multiple sets of one or more LEDdevices as a mask in a first direction; patterning the elastomeric layerusing the patterned photoresist layer as a mask in a second directionthat is opposite the first direction; after patterning the elastomericlayer, removing the filling material and the patterned photoresistlayer, thereby revealing the multiple sets of one or more LED deviceshaving the patterned elastomeric layer deposited thereon.
 9. The methodof claim 8, wherein patterning the photoresist layer comprisestransmitting light through the elastomeric layer toward the photoresistlayer.
 10. The method of claim 8, wherein patterning the elastomericlayer comprises etching the elastomeric layer.
 11. A display systemfabricated by a method comprising: obtaining a set of one or morelight-emitting diode (LED) devices having one or more elastomericinterfaces deposited on a light-outputting side of the set of one ormore LED devices; using a pick-up tool to: form one or more opticalelements in the one or more elastomeric interfaces by pressing thepick-up tool against the one or more elastomeric interfaces; and pick upand place the set of one or more LED devices onto a target substrate;separating the pick-up tool from the one or more elastomeric interfaces,thereby revealing the one or more optical elements formed on the set ofone or more LED devices.
 12. The display system of claim 11, wherein theone or more optical elements are formed in the one or more elastomericinterfaces before the set of one or more LED devices is picked up andplaced onto the target substrate.
 13. The display system of claim 11,wherein the one or more optical elements are formed in the one or moreelastomeric interfaces after the set of one or more LED devices ispicked up but as the set of one or more LED devices is being placed ontothe target substrate.
 14. The display system of claim 11 fabricated bythe method, the method further comprising: removing, from the one ormore elastomeric interfaces, elastomeric material surrounding the one ormore optical elements.
 15. The display system of claim 11, wherein theset of one or more LED devices comprises a plurality of unsingulated LEDdevices.
 16. The display system of claim 11, wherein the set of one ormore optical elements includes at least one of a group comprising alens, a waveguide, and a diffraction grating.
 17. The display system ofclaim 11, wherein obtaining the set of one or more LED devices havingthe one or more elastomeric interfaces comprises: obtaining a layeredstructure that includes an embedded layer comprising multiple sets ofone or more LED devices embedded in a filling material, an elastomericlayer deposited on the embedded layer, and a photoresist layer depositedon the elastomeric layer; patterning the photoresist layer by using themultiple sets of one or more LED devices as a mask in a first direction;patterning the elastomeric layer using the patterned photoresist layeras a mask in a second direction that is opposite the first direction;after patterning the elastomeric layer, removing the filling materialand the patterned photoresist layer, thereby revealing the multiple setsof one or more LED devices having the patterned elastomeric layerdeposited thereon.
 18. A non-transitory computer-readable storage mediumstoring processor-executable instructions for: obtaining a set of one ormore light-emitting diode (LED) devices having one or more elastomericinterfaces deposited on a light-outputting side of the set of one ormore LED devices; using a pick-up tool to: form one or more opticalelements in the one or more elastomeric interfaces by pressing thepick-up tool against the one or more elastomeric interfaces; and pick upand place the set of one or more LED devices onto a target substrate;separating the pick-up tool from the one or more elastomeric interfaces,thereby revealing the one or more optical elements formed on the set ofone or more LED devices.
 19. The non-transitory computer-readablestorage medium of claim 18, wherein the one or more optical elements areformed in the one or more elastomeric interfaces before the set of oneor more LED devices is picked up and placed onto the target substrate.20. The non-transitory computer-readable storage medium of claim 18,wherein the one or more optical elements are formed in the one or moreelastomeric interfaces after the set of one or more LED devices ispicked up but as the set of one or more LED devices is being placed ontothe target substrate.